The objective of this proposal is a biochemical and morphological study of the development of the blood-ocular barriers to proteins in the embryonic and post-embryonic chicken. We are investigating the mechanisms responsible for the decline in vitreous humor protein concentration in the final third of chicken embryo development. Embryonic plasma proteins are being purified and labelled with 125I or used for the production of specific antibodies. These preparations will be used to quantitate changes in the concentration of specific plasma proteins in the vitreous humor and to localize the routes of entry of these proteins into the eye. In addition, light and electron microscopy has been used to map the routes of penetration of the enzyme tracers microperoxidases (1,880 MW), horseradish peroxidase (40,000 MW) and catalase (240,000 MW) from the vascular system into the vitreous and aqueous humor of embryonic and hatched chickens. As part of these studies, we are describing the functional development of the aqueous outflow system by intraocular injection of peroxidase and fluorescein into embryos of different ages. These experiments are providing a systematic study of the development of the blood-ocular barriers to proteins and should contribute to an understanding of the breakdown or absence of one or more of these barriers in many ocular diseases.